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Jun 30, 2018
06/18

by
Yang Gao; Hwang Lee

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We investigate the quantum Cramer-Rao bounds on the joint multiple-parameter estimation with the Gaussian state as a probe. We derive the explicit right logarithmic derivative and symmetric logarithmic derivative operators in such a situation. We compute the corresponding quantum Fisher information matrices, and find that they can be fully expressed in terms of the mean displacement and covariance matrix of the Gaussian state. Finally, we give some examples to show the utility of our analytical...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1407.7352

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Jun 26, 2018
06/18

by
Morgan W. Mitchell

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We describe the generation of atom-resonant indistinguishable photon pairs using nonlinear optical techniques, their spectral purification using atomic filters, characterization using multi-photon interference, and application to quantum-enhanced sensing with atoms. Using either type-I or type-II cavity-enhanced spontaneous parametric down-conversion, we generate pairs of photons in the resonant modes of optical cavities with linewidths comparable to the 6 MHz natural linewidth of the D$_1$...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1502.07615

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Jun 30, 2018
06/18

by
Muhammad H. Ahmed; Andrew D. Greentree

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High fidelity quantum information transport is necessary for most practical models of quantum computation. By analogy with optical wave guides, a spatio-temporally varying magnetic potential on a one dimensional spin chain can achieve high fidelity transport of spin excitations. By comparing different potential shapes, we establish the effects of potential shape on the fidelity and transport speed. We incorporate disorder into our model and show methods to minimise its effect on transport....

Topic: Quantum Physics

Source: http://arxiv.org/abs/1411.7749

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Jun 30, 2018
06/18

by
Keith R. Motes; Alexei Gilchrist; Jonathan P. Dowling; Peter P. Rohde

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We present an architecture for arbitrarily scalable boson-sampling using two nested fiber loops. The architecture has fixed experimental complexity, irrespective of the size of the desired interferometer, whose scale is limited only by fiber and switch loss rates. The architecture employs time-bin encoding, whereby the incident photons form a pulse train, which enters the loops. Dynamically controlled loop coupling ratios allow the construction of the arbitrary linear optics interferometers...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1403.4007

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Jun 30, 2018
06/18

by
Muhammad Nadeem

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In this paper, we propose quantum position-verification schemes where all the channels are untrusted except the position of the prover and distant reference stations of verifiers. We review and analyze the existing QPV schemes containing some pre-shared data between the prover and verifiers. Most of these schemes are based on non-cryptographic assumptions, that is, quantum/classical channels between the verifiers are secure. It seems impractical in the environment fully controlled by...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1403.5925

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Jun 30, 2018
06/18

by
Kenneth Rudinger; Robert Joynt

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In engineered quantum systems, the Hamiltonian is often not completely known and needs to be determined experimentally with accuracy and efficiency. We show that this may be done at temperatures that are greater than the characteristic interaction energies, but not too much greater. The condition for this is that there are not too many interactions: the Hamiltonian is sparse in a well-defined sense. The protocol that accomplishes this is related to compressed sensing methods of classical signal...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1410.3029

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Jun 27, 2018
06/18

by
Nayeli Azucena Rodriguez-Briones; Jun Li; Xinhua Peng; Tal Mor; Yossi Weinstein; Raymond Laflamme

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In a recent paper, PRL 114 100404, 2015, Raeisi and Mosca gave a limit for cooling with Heat-Bath Algorithmic Cooling (HBAC). Here we show how to exceed that limit by having correlation in the qubits-bath interaction.

Topic: Quantum Physics

Source: http://arxiv.org/abs/1506.01778

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Jun 28, 2018
06/18

by
Ämin Baumeler; Stefan Wolf

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Classical correlations without predefined causal order arise from processes where parties manipulate random variables, and where the order of these interactions is not predefined. No assumption on the causal order of the parties is made, but the processes are restricted to be logically consistent under any choice of the parties' operations. It is known that for three parties or more, this set of processes is larger than the set of processes achievable in a predefined ordering of the parties....

Topic: Quantum Physics

Source: http://arxiv.org/abs/1507.01714

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Jun 30, 2018
06/18

by
Alexandre Roulet; Huy Nguyen Le; Valerio Scarani

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Optical emitters strongly coupled to photons propagating in one-dimensional waveguides are a promising platform for optical quantum information processing. Here, we present a theoretical study of the scattering of two indistinguishable photons on a single two-level atom in a Hong-Ou-Mandel set-up. By computing the dynamics, we can describe the system at any time of the scattering event. This allows us to highlight the one-to-one correspondence between the saturation of the atom and the...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1411.6411

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Jun 30, 2018
06/18

by
Nedasadat Hosseinidehaj; Robert Malaney

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In this work we analyze a quantum communication scheme for entanglement-based continuous variable quantum key distribution between two ground stations. Communication occurs via a satellite over two independent atmospheric fading channels dominated by turbulence-induced beam wander. In this scheme the engineering complexity remains largely on the ground transceivers, with the satellite acting simply as a reflector. We show how the use of a highly selective post-selection strategy may lead to a...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1411.3153

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Jun 30, 2018
06/18

by
Leonardo Guerini

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This Master's thesis has two central subjects: the simulation of correlations generated by local measurements on entangled quantum states by local hidden-variables models and the revelation of hidden nonlocality. We present and detail the Werner's local model and the hidden nonlocality of some Werner states of dimension $d\geq5$, the Gisin-Degorre's local model for a Werner state of dimension $d=2$ and the local model of Hirsch et al. for mixtures of the singlet state and noise, all of them for...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1407.5958

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Jun 30, 2018
06/18

by
Ci Li; Xizheng Zhang; Zhi Song

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A hybrid quantum system combines two or more distinct quantum components, exhibiting features not seen in these individual systems. In this work, we study the one-dimensional Jaynes-Cummings- Hubbard model in the two-excitation subspace. We find that the center momentum of two-excitation induces a magnetic ux piercing the 4-leg ladder in the auxiliary space. Furthermore, it is shown that the system in {\pi}-center-momentum subspace is equivalent to a chain system for spin-1 particle with...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1409.7161

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Jun 30, 2018
06/18

by
Li-Wei Yu; Mo-Lin Ge

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A new realization of doubling degeneracy based on emergent Majorana operator $\Gamma$ presented by Lee-Wilczek has been made. The Hamiltonian can be obtained through the new type of solution of Yang-Baxter equation, i.e. $\breve{R}(\theta)$-matrix. For 2-body interaction, $\breve{R}(\theta)$ gives the "superconducting" chain that is the same as 1D Kitaev chain model. The 3-body Hamiltonian commuting with $\Gamma$ is derived by 3-body $\breve{R}_{123}$-matrix, we thus show that the...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1409.3396

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Jun 29, 2018
06/18

by
Michael J. W. Hall; Arun Kumar Pati; Junde Wu

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The products of weak values of quantum observables are shown to be of value in deriving quantum uncertainty and complementarity relations, for both weak and strong measurement statistics. First, a 'product representation formula' allows the standard Heisenberg uncertainty relation to be derived from a classical uncertainty relation for complex random variables. We show this formula also leads to strong uncertainty relations for unitary operators, and underlies an interpretation of weak values...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1603.05776

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Jun 29, 2018
06/18

by
I. G. da Paz; Rodolfo Soldati; L. A. Cabral; J. G. G. de Oliveira; Marcos Sampaio

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Recently there have been experimental results on Poisson spot matter wave interferometry followed by theoretical models describing the relative importance of the wave and particle behaviors for the phenomenon. We propose an analytical theoretical model for the Poisson's spot with matter waves based on Babinet principle in which we use the results for a free propagation and single slit diffraction. We take into account effects of loss of coherence and finite detection area using the propagator...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1609.09023

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Jun 28, 2018
06/18

by
Keyu Xia

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Entangled continuous variable (CV) Gaussian states with different wavelengths plays a central role in recent CV-based approaches to quantum network, quantum information processing and quantum metrology. Typically, experiments demonstrating CV entanglement exploit the optical parametric frequency down conversion. Due to the probabilistic nature of photon pair generation, the entanglement involving the post-selection of photonic qubits is limited to at most three colors. Here We theoretically...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1507.07310

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Jun 29, 2018
06/18

by
Adam Zaman Chaudhry

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A general treatment of the quantum Zeno and anti-Zeno effects is presented which is valid for an arbitrary system-environment model in the weak system-environment coupling regime. It is shown that the effective lifetime of a quantum state that is subjected to repeated projective measurements depends on the overlap of the spectral density of the environment and a generalized `filter function' which in turn depends on the system state that is repeatedly being prepared, the measurement interval,...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1604.06561

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Jun 29, 2018
06/18

by
Todd Brun; Min-Hsiu Hsieh

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We provide a self-contained introduction for entanglement-assisted quantum error-correcting codes in this book chapter.

Topic: Quantum Physics

Source: http://arxiv.org/abs/1610.04013

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Jun 29, 2018
06/18

by
D. Z. Rossatto; C. J. Villas-Boas

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Recently it was shown that the quantum behavior of an intense cavity field can be revealed by measuring the steady atomic correlations between two ideal atoms, which interact with the same leaking cavity mode. Considering a weak atom-field coupling regime and large average number of photons in the cavity mode ($\bar{n}$), one expects that a semiclassical theory could explain the whole dynamics of the system. However, this system presents the generation of correlations between the atoms, which...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1605.09472

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Jun 30, 2018
06/18

by
Giuseppe Vallone; Davide Marangon; Matteo Canale; Ilaria Savorgnan; Davide Bacco; Mauro Barbieri; Simon Calimani; Cesare Barbieri; Nicola Laurenti; Paolo Villoresi

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Quantum Key Distribution (QKD) allows to share random keys between two users with unconditional security: the key is usually generated by exchanging a stream of photons. The long-term vision of QKD is represented by a quantum network, implemented by fiber and free-space links involving ground and/or satellites stations. The presence of the atmospheric turbulence represents an obstacle for free-space quantum communications, due to the increase of optical losses. Here we introduce a method to...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1404.1272

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Jun 30, 2018
06/18

by
Ángel Rivas; Markus Müller

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Understanding the role of correlations in quantum systems is both a fundamental challenge as well as of high practical relevance for the control of multi-particle quantum systems. Whereas a lot of research has been devoted to study the various types of correlations that can be present in the states of quantum systems, in this work we introduce a general and rigorous method to quantify the amount of correlations in the dynamics of quantum systems. Using a resource-theoretical approach, we...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1409.1770

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Jun 29, 2018
06/18

by
Simon J. Devitt

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The task of programming a quantum computer is just as strange as quantum mechanics itself. But it now looks like a simple 3D puzzle may be the future tool of quantum software engineers.

Topic: Quantum Physics

Source: http://arxiv.org/abs/1609.06628

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Jun 30, 2018
06/18

by
V. Chithiika Ruby; M. Senthilvelan

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We construct photon modulated coherent states of a generalized isotonic oscillator by expanding the newly introduced superposed operator through Weyl ordering method. We evaluate the parameter $A_3$ and the $s$-parameterized quasi probability distribution function to confirm the non - classical nature of the states. We also calculate the identities related with the quadrature squeezing to explore the squeezing property of the states. Finally, we investigate the fidelity between the photon...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1405.2710

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Jun 30, 2018
06/18

by
Katarzyna Macieszczak

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We derive upper bounds on the quantum Fisher information in interferometry with $N$ subsystems, e.g. two-level atoms or Gaussian modes, in the presence of arbitrarily correlated Gaussian dephasing including independent and collective dephasing. The derived upper bound enables us to analyse the Fisher information asymptotic behaviour when $N\rightarrow\infty$. Dephasing introduces random phases to subsystems dynamics, which lowers the precision of estimating the phase difference $\phi$ in an...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1403.0955

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Jun 29, 2018
06/18

by
Raju Valivarthi; Marcel. li Grimau Puigibert; Qiang Zhou; Gabriel H. Aguilar; Varun B. Verma; Francesco Marsili; Matthew D. Shaw; Sae Woo Nam; Daniel Oblak; Wolfgang Tittel

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If a photon interacts with a member of an entangled photon pair via a so-called Bell-state measurement (BSM), its state is teleported over principally arbitrary distances onto the second member of the pair. Starting in 1997, this puzzling prediction of quantum mechanics has been demonstrated many times; however, with one very recent exception, only the photon that received the teleported state, if any, travelled far while the photons partaking in the BSM were always measured closely to where...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1605.08814

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Jun 28, 2018
06/18

by
Yan-Ling Wang; Mao-Sheng Li; Zhu-Jun Zheng; Shao-Ming Fei

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We study the local indistinguishability of mutually orthogonal product basis quantum states in the high-dimensional quantum system. In the quantum system of $\mathbb{C}^d\otimes\mathbb{C}^d$, where $d$ is odd, Zhang \emph{et al} have constructed $d^2$ orthogonal product basis quantum states which are locally indistinguishable in [Phys. Rev. A. {\bf 90}, 022313(2014)]. We find a subset contains with $6d-9$ orthogonal product states which are still locally indistinguishable. Then we generalize...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1509.06927

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Jun 29, 2018
06/18

by
Kishore Thapliyal; Rishi Dutt Sharma; Anirban Pathak

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Recently Tian, Zhang and Li (TZL) have proposed a protocol for voting based on controlled quantum teleportation (Int. J. Theor. Phys. DOI 10.1007/s10773-015-2868-8). We have critically analyzed the protocol and have shown that it's neither efficient nor secure. Further, it is shown that in the TZL protocol, the scrutineer Charlie does not have the required control over the voting process. Apart from showing the limitations of TZL protocol, two improved protocols for quantum voting along the...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1602.00791

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Jun 28, 2018
06/18

by
Pedro H. F. Nogueira; Antonio S. de Castro

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The literature on the exponential Fourier approach to the one-dimensional quantum harmonic oscillator problem is revised and criticized. It is shown that the solution of this problem has been built on faulty premises. The problem is revisited via the Fourier sine and cosine transform method and the stationary states are properly determined by requiring definite parity and square-integrable eigenfunctions.

Topic: Quantum Physics

Source: http://arxiv.org/abs/1511.03228

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Jun 29, 2018
06/18

by
Chun-Yao Yang; Chun Lin; Charlotte Liljestrand; Wei-Min Su; Carlota Canalias; Chih-Sung Chuu

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Quasi-phase-matching (QPM) has enriched the capacity of parametric down-conversion (PDC) in generating biphotons for many fundamental tests and advanced applications. However, it is not clear how the nonidealities and randomness in the QPM grating of a parametric down-converter may affect the quantum properties of the biphotons. This paper intends to provide insights into the interplay between PDC and nonideal or random QPM structures. Using a periodically poled nonlinear crystal with short...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1605.05083

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Jun 30, 2018
06/18

by
Min Namkung; Jinho Chang; Jaehee Shin; Younghun Kwon

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In this article, we investigate the error bound of quantum discord, obtained by the analytic formula of Ali et al.[Phys. Rev. A 81(2010), 042105] in case of general X states and by the analytic formula of Fanchini et al.[Phys. Rev. A 81(2010), 052107] in case of symmetric X states. We show that results of Ali et. al. to general X states and Fanchini et al. to symmetric X states may have worst-case error of 0.004565 and 0.0009 respectively.

Topic: Quantum Physics

Source: http://arxiv.org/abs/1404.6329

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Jun 26, 2018
06/18

by
Shelby Kimmel; Guang Hao Low; Theodore J. Yoder

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An important step in building a quantum computer is calibrating experimentally implemented quantum gates to produce operations that are close to ideal unitaries. The calibration step involves estimating the systematic errors in gates and then using controls to correct the implementation. Quantum process tomography is a standard technique for estimating these errors, but is both time consuming, (when one only wants to learn a few key parameters), and is usually inaccurate without resources like...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1502.02677

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Jun 30, 2018
06/18

by
Faheel Ather Hashmi; Shi-Yao Zhu

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We investigate the influence of the additional third level on the dynamic evolution of a Two-Level system interacting with a coherent field in the strong coupling regime where Rotating Wave Approximation is not valid. We find that the additional level has great influence on the evolution of the system population. Our results show that the Two-Level model is not a good approximation in this strong light-matter coupling regime. We further investigate the parameter space where the Two-Level model...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1406.0250

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Jun 30, 2018
06/18

by
Ariel Bendersky; Gonzalo de la Torre; Gabriel Senno; Santiago Figueira; Antonio Acin

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The Church-Turing thesis is one of the pillars of computer science; it postulates that every classical system has equivalent computability power to the so-called Turing machine. While this thesis is crucial for our understanding of computing devices, its implications in other scientific fields have hardly been explored. Here we start this research programme in the context of quantum physics and show that computer science laws have profound implications for some of the most fundamental results...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1407.0604

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Jun 30, 2018
06/18

by
Giuseppe Davide Paparo; Vedran Dunjko; Adi Makmal; Miguel Angel Martin-Delgado; Hans J. Briegel

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Can quantum mechanics help us in building intelligent robots and agents? One of the defining characteristics of intelligent behavior is the capacity to learn from experience. However, a major bottleneck for agents to learn in any real-life situation is the size and complexity of the corresponding task environment. Owing to, e.g., a large space of possible strategies, learning is typically slow. Even for a moderate task environment, it may simply take too long to rationally respond to a given...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1401.4997

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Jun 28, 2018
06/18

by
Rafael Chaves

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It is a recent realization that many of the concepts and tools of causal discovery in machine learning are highly relevant to problems in quantum information, in particular quantum nonlocality. The crucial ingredient in the connection between both fields is the tool of Bayesian networks, a graphical model used to reason about probabilistic causation. Indeed, Bell's theorem concerns a particular kind of a Bayesian network and Bell inequalities are a special case of linear constraints following...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1506.04325

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Jun 30, 2018
06/18

by
Marcin Jarzyna

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In most communication scenarios, sending a symbol encoded in a quantum state requires spending resources such as energy, which can be quantified by a cost of communication. A standard approach in this context is to quantify the performance of communication protocol by classical capacity, quantifying the maximal amount of information that can be transmitted through a quantum channel per single use of the channel. However, different figures of merit are also possible, and a particularly...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1704.06696

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Jun 30, 2018
06/18

by
Keyu Xia; Jason Twamley

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We propose a design for a quantum interface exploiting the electron spins in crystals to swap the quantum states between the optical and microwave. Using sideband driving of a superconducting flux qubit and a combined cavity/solid-state spin ensemble Raman transition, we demonstrate how a stimulated Raman adiabatic passage (STIRAP)-type operation can swap the quantum state between a superconducting flux qubit and an optical cavity mode with a fidelity higher than $90\%$. We further consider two...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1408.5972

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Jun 30, 2018
06/18

by
Isaac H. Kim

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A one-dimensional quantum simulator can simulate two-dimensional quantum many-body systems. A representation of a low-energy state is obtained by applying a feedback loop.

Topic: Quantum Physics

Source: http://arxiv.org/abs/1702.02093

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Jun 30, 2018
06/18

by
David Gelbwaser-Klimovsky; Gershon Kurizki

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We analyze work extraction from an autonomous (self-contained) heat-powered optomechanical setup. The initial state of the quantized mechanical oscillator plays a key role. As the initial mean amplitude of the oscillator decreases, the resulting efficiency increases. In contrast to laser-powered self-induced oscillations, work extraction from a broadband heat bath does not require coherence or phase-locking: an initial phase-averaged coherent state of the oscillator still yields work, as...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1410.8561

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Jun 29, 2018
06/18

by
Costantino Budroni; Nikolai Miklin; Rafael Chaves

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We investigate the possibility of distinguishing among different causal relations starting from a limited set of marginals. Our main tool is the notion of adhesivity, that is, the extension of probability or entropies defined only on subsets of variables, which provides additional independence constraints among them. Our results provide a criterion for recognizing which causal structures are indistinguishable when only limited marginal information is accessible. Furthermore, the existence of...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1607.08540

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Jun 30, 2018
06/18

by
Francisco M. Fernández

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We analyze earlier applications of perturbation theory by the moment method (also called inner product method) to anharmonic oscillators. For concreteness we focus on two-dimensional models with symmetry $C_{4v}$ and $C_{2v}$ and reveal the reason why some of those earlier treatments proved unsuitable for the calculation of the perturbation corrections for some excited states. Point-group symmetry enables one to predict which states require special treatment.

Topic: Quantum Physics

Source: http://arxiv.org/abs/1409.4120

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Jun 28, 2018
06/18

by
Hisashi Ogawa; Hideaki Ohdan; Kazunori Miyata; Masahiro Taguchi; Kenzo Makino; Hidehiro Yonezawa; Jun-ichi Yoshikawa; Akira Furusawa

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Real-time controls based on quantum measurements are powerful tools for various quantum protocols. However, their experimental realization have been limited by mode-mismatch between temporal mode of quadrature measurement and that heralded by photon detection. Here, we demonstrate real-time quadrature measurement of a single-photon wavepacket induced by a photon detection, by utilizing continuous temporal-mode-matching between homodyne detection and an exponentially rising temporal mode. Single...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1507.06172

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Jun 29, 2018
06/18

by
Qian Wang; H. T. Quan

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Based on previous studies in a single particle system in both the integrable [Jarzynski, Quan, and Rahav, Phys.~Rev.~X {\bf 5}, 031038 (2015)] and the chaotic systems [Zhu, Gong, Wu, and Quan, Phys.~Rev.~E {\bf 93}, 062108 (2016)], we study the the correspondence principle between quantum and classical work distributions in a quantum many-body system. Even though the interaction and the indistinguishability of identical particles increase the complexity of the system, we find that for a quantum...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1612.05692

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Jun 30, 2018
06/18

by
T. Hashimoto; A. Hayashi; M. Horibe

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For a qudit, a quantum system on a finite dimensional Hilbert space, we construct minimum uncertainty states and a non-negative quasi probability distribution. They are the discrete version of the coherent states and the Husimi function in the continuous quantum mechanics. The two bases related by the discrete Fourier transformation are identified with the position and momentum bases. We prove an inequality concerning uncertainties of the position and momentum of a qudit. The minimum...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1704.03222

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Jun 29, 2018
06/18

by
A. A. Strakhov; V. I. Man'ko

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We construct the positive invertible map of the mixed states of a single qutrit onto the states of two identical fermions. It is shown that using this one-to-one correspondence between qutrit states and states of two identical three-dimensional fermions (the unphysical odd dimension is picked for simplicity) one may attribute hidden entanglement to a single mixed state of qutrit.

Topic: Quantum Physics

Source: http://arxiv.org/abs/1605.08816

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Jun 29, 2018
06/18

by
F. R. de S. Nunes; J. J. I. de Souza; D. A. Souza; R. C. Viana; O. P. de Sá Neto

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In this work we describe a scheme to perform a continuous over time quantum non demolition (QND) mea- surement of the number of phonons of a nanoelectromechanical system (NEMS). Our scheme also allows us to describe the statistics of the number of phonons.

Topic: Quantum Physics

Source: http://arxiv.org/abs/1601.03750

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Jun 30, 2018
06/18

by
Alexander Streltsov; Soojoon Lee; Gerardo Adesso

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We introduce the concentrated information of tripartite quantum states. For three parties Alice, Bob, and Charlie, it is defined as the maximal mutual information achievable between Alice and Charlie via local operations and classical communication performed by Charlie and Bob. We derive upper and lower bounds to the concentrated information, and obtain a closed expression for it on several classes of states including arbitrary pure tripartite states in the asymptotic setting. We show that...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1410.6346

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Jun 29, 2018
06/18

by
Simon James Daniel Phoenix

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The mutual information has been successfully used as a measure of correlation strength between quantum systems, especially for bipartite systems. Here we examine the use of this measure for multipartite quantum systems. For system of qubits we find that the difference between `classical' and `quantum' regimes of correlation strength amounts to just 1 bit of information, at most. We show that the information content of a correlation can be expanded into correlations between pairwise components...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1610.00105

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Jun 27, 2018
06/18

by
Matteo A. C. Rossi; Matteo G. A. Paris

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We address the use of entangled qubits as quantum probes to characterize the dynamical noise induced by complex environments. In particular, we show that entangled probes improve estimation of the correlation time for a broad class of environmental noises compared to any sequential strategy involving single qubit preparation. The effect is present when the noise is faster than a threshold value, a regime which may always be achieved by tuning the coupling between the quantum probe and the...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1503.03402

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Jun 30, 2018
06/18

by
Marina Mondin; Fred Daneshgaran; Inam Bari; Maria Teresa Delgado; Stefano Olivares; Matteo G. A. Paris

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We address photon-number-assisted, polarization- based, binary communication systems equipped with photon counting receivers. In these channels information is encoded in the value of polarization phase-shift but the carrier has and additional degree of freedom, i.e. its photon distribution, which may be exploited to implement binary input-multiple output (BIMO) channels also in the presence of a phase-diffusion noise affecting the polarization. Here we analyze the performances of these...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1412.1104